Brake power controller with electrically actuated locking apparatus

ABSTRACT

A brake pressure proportioning controller is described for the rear wheel brakes of an automotive vehicle with a brake unit equipped with an anti-locking control, the brake pressure controller being provided with a lockout arrangement in which an electromagnetic drive prevents the brake pressure controller from performing its pressure reducing function as long as the anti-locking control is functioning. The lockout arrangement includes an actuating element (6) which is axially slidable by the drive (1), an intermediate bushing (8) is formed with radial round holes (34, 34&#39;) in which interlocking ball elements (31, 31&#39;) are guided in radial directions which are thicker than the wall of the intermediate bushing (8) and which are normally retained by the actuating element (6) in a position in which they lock any axial movement of the control element (9) in the direction of the electromagnetic drive (1). In the event of an anti-locking control failure, actuating element (96) is slid axially such that it is capable of accommodating the interlocking elements (31, 31&#39;) in a radial recess ( 7) is released. The lockout arrangement is located outside the hydraulic brake circuit.

BACKGROUND OF THE INVENTION

The invention is related to a rear brake pressure proportioning valve orcontroller having an electrically actuated lockout arrangement.

Various brake pressure proportioning valves or controllers have beenproposed in which an electromagnetically moved tappet extends through anaxial bore in a pressure control piston, keeping the closing member ofthe control valve spaced from its valve seat as long as the anti-lockingcontrol is operational. An increased degree of safety is attained by theadditional incorporation of such a controller since the brake pressureacting on the rear wheels is thus reduced when the anti-locking controlmalfunctions.

Starting from this principle, the present invention has the object tocreate further functional improvements, in particular, low forceactuation of the lockout arrangement. This is of the special importancein case of twin-type brake power controllers for a diagonal combinationof the brake circuits in order to allow locking out and releasing bothbrake circuits by a single actuator.

SUMMARY OF THE INVENTION

This object is achieved by an electromagnetically driven locking pinnormally held in an axially shifted lockout position intermediateradially movable locking elements. The locking elements are received inopenings in a fixed member and engaged by a radially acting wedgingsurface on a spring urged valve actuator member, which prevents axialclosing movement of the valve control piston, initially positioned inthe open position, as long as locking pin is held in its shiftedposition. The locking pin is released when an antiskid control fails bydeenergization of the electromagnetic drive, and radial movement of thelocking elements is allowed, so that normal proportioning action occursby closing movement of the valve control piston. Due to the exclusivelyradial locking direction, unlocking is enabled with small forces. Uponrepair of the anti-locking control, the controller valve member iseasily locked again, because the brake lines will then be unpressurizedand the control piston shifted to the open position by a spring, theinterlocking elements easily moved radially out by the locking pin toagain engage the wedge surface of the valve actuating element.

This set-up of the lockout arrangement is suited especially well fortwin-type controllers because an electromagnet in common furnishessufficient force to lock both control units.

The change-over pressure of the controller may be set, as loaddependently by substituting for the control spring which generates afixed bias force which acts upon the valving control piston a loadvariable force generating mechanical, pneumatic, hydraulic orelectromagnet means.

A solution which provides particularly reliable lock out operation isachieved by locating the components of the arrangement in a chamberoutside the hydraulic control circuit. A sophisticated and expensivesealing of the lockout arrangement is thus not needed.

That is, in lieu of a direct actuation of valve closing members by meansof a tappet--as proposed in past solutions--the control piston orcontrol pistons are directly acted upon in the present invention, eachcontrol piston sealedly projecting out of its bore into a chamberhousing the lockout arrangement, which chamber is free of pressurefluid.

If and when the anti-locking control fails during operation of thebrakes, the full pressure will exist at the outlet since the controlleris locked until then.

Although the control piston will immediately travel into its pressurereducing position, the output pressure already existing would lock therear wheel brakes if it were not reduced. For this reason, an additionalpressure reducing apparatus is expedient which brings about an increaseof the volume of the outlet-side section of the bore when the valve inthe control piston is closed. At the least, the stroke of the controlpiston in the unlocked condition should definitely be larger than theclosing travel of the valve of the control piston to achieve theincreased volume of the outlet side section of the bore.

Further advantageous features will be revealed by the followingdescription of the preferred embodiment making reference to anaccompanying drawing.

DESCRIPTION OF THE DRAWING

The Figure shows a twin-type brake power controller in partial section,with the right half of the Figure illustrating the position of theelements when the anti-locking control is properly functioning, and theleft half of the Figure illustrating the positions assumed after failureof the anti-locking control.

DETAILED DESCRIPTION

The lockout arrangement of this controller includes an electromagneticdrive 1 including an electromagnetic coil 2 which is supplied with acontrol current I from an antilock control, and which surrounds themagnetic core 3, staked so as to be fixed to the housing. A magneticarmature 5 is subjected to the action of a compression spring 4 and ismovable axially. The magnetic armature 5 is press fit to the actuatingelement 6 which is piston-shaped and is provided with a radialring-shaped groove 7 with beveled edges. The actuating element 6 extendsthrough the intermediate bushing 8 which is fixed to the housing. Thebushing 8 is formed with two radial round holes 34 and 34' which arepositioned opposite each other and in each of which a ball-shapedinterlocking element 31, 31' is radially guided. The control element 9has a cup-shaped configuration and is furnished with a control finger 10at its bottom. The inside wall of the cup-shaped part of said controlelement 9 is provided with a tapered wedging extension step 11 towardthe opening. The cup-shaped part of the control element 9 axiallyslidingly receives a part of the intermediate bushing 8.

The control element 9 is subject to a control force for the adjustmentof the change-over pressure of the brake pressure controller. At theoutside wall of the control element 9, the illustrated design versionwith a fixedly adjusted change-over pressure has a circumferentialradial projection 12 which is subjected through the annular disc 13 tothe force of the control spring 14. The control finger 10 is shaped asan acute-angled cone with a rounded tip 16 which acts upon thetransmission element 15 by an abutment within a depression 17 of thetransmission element 15. The depression also is configured as anacute-angled cone with rounded tip whose curvature is adapted to that ofthe tip 16 of the control finger 10 and whose apex angle is larger thanthat of the control finger 10.

Acting as a balance beam having its balance point at the tip 16 of thecontrol finger 10, the control element 15 acts on each of two balls 18and 18' and upon two associated control pistons 19 and 19'. The latterare each guided axially within respective stepped bores 20, 20' andproject through the guide bushings 21 and 21' fixed to the housing, intothe chamber 22 which is free of pressure fluid and contains thetransmission element 15.

With the aid of the sealing sleeves 23 and 23', the control pistons 19and 19' are sealed off in respect of the guide bushings 21, 21', whichare themselves provided with sealing rings 24 and 24' to be sealed withrespect to the walls of the bores 20, 20'.

At the ends of the control pistons 19 and 19' facing away from theactuating and locking apparatus, the valve seats 25 and 25' arepositioned which interact with the respective closing members 26, 26'.The latter are each located within a cavity 29 or 29' within the lowerend of the control pistons 19 and 19' and are subject to the action ofthe compression springs 30, 30' urging them in the direction of thevalve seats 25, 25'. These valves form the only pressure fluid passagefrom the inlets 27 and 27' to the respective outlets 28, 28'.

For the explanation of the functioning of the invention, reference ismade first of all to the right half of the Figure. In the initialposition, the brake system is unpressurized, so that spring 14 shiftscontrol element 9 to the fully down position shown. If the anti-lockingcontrol is operating normally, and control current I flows, the coil 2holds the magnetic armature 5 up by the attraction of its magneticfield, against the force of the compression spring 4. The actuatingelement 6 is, therefore, held in an axial position in which it locks theinterlocking ball elements 31, in a radially outward location such thatthey are held abutted against the wedging extension step 11 of thecontrol element 9. Thus any axial movement of the control element 9toward the drive 1 is positively prevented.

Acting through the transmission element 15 and the respective balls 18,18', the control element 9 retains both control pistons 19 and 19' in adownward axial position in which the respective ball closing members 26,26' are positioned above the valves seats 25, 25' because the tappets 32and 32' are in abutment against the front walls 33, 33' of the bores 20and 20', keeping the closing members 26 and 26' spaced from the valveseats 25 and 25'.

In this context, it is of importance that the control pistons 19 and 19'are not abutted against the front walls 33 and 33' in order that evenwith the controller locked out they are afforded a slight axial movementwhen the change-over pressure is reached. In this way it is safeguardedthat the control pistons do not stick and remain operative, even thoughheld in this position over a very extended period, as this is the normalcondition.

In this locked position, the output pressure Pa equals the inputpressure Pe.

The left half of the Figure shows the brake pressure controller in thepressure reducing position, that is to say, the anti-locking control hasmet with a failure, which failure causes a shut off of the electricalcurrent I and the coil 2 is thus in the de-energized condition.

The actuating element 6 is slid by the compression spring 4 into aposition in which the ring-shaped groove 7 can accommodate theinterlocking elements 31 and 31' to such an extent that the axial slideof the control element 9 toward the drive 1 is unimpeded.

As soon as the change-over pressure set by the control spring 14 hasbeen reached, the brake pressure controller starts its pressure reducingfunction. The control pistons 19 and 19', acted on by the pressure Pe'exerted on the larger diameter on the side of the spring 14, and by thepressure Pa' acting on the full area below the pistons 19, 19', willslide into the position illustrated in this left half of the Figure, sothat the closing members 26 and 26' rest sealingly on the valve seats25, respectively 25' because the control pistons 19 and 19' havetraveled away from the front walls 33 and 33' and the tappets 32 and 32'are no longer abutted against the latter. As the input pressure Pe'rises further the control piston 19 and 19' will travel up and down in arapid succession and will thereby reduce the output pressure Pa' to aproportion of the input pressure Pe'. The control pistons 19, 19' areseen to be shifted upward from the initial full down position withmembers 26, 26' fully open so that the volume of the section of thebores 20, 20' at the outlet 28 28' is increased to reduce the pressurePa, Pa' when the anti lock control fails, as discussed above. A separatepressure reducing device can be used for this purpose, as also discussedabove.

We claim:
 1. A brake pressure proportioning controller toproportionately reduce the pressure to the rear wheel brakes of anautomotive vehicle equipped with an anti-locking control, said brakepressure controller being provided with a lockout control arrangementwhich prevents the brake pressure controller from performing a pressurereducing function as long as said anti-locking control is functioning,said lockout arrangement including an electromagnetic actuator having amagnetic coil, with an electrical current flowing to energize said drivecoil as long said wheel brake anti-locking control is functioning, saidlockout arrangement further including an actuating element axiallyslidable by energizing of said coil to a locking position, said brakingpressure controller including an axially shiftable control elementaxially moved during operation of said braking pressure controller, saidlockout arrangement further including radially movable interlockingelements radially positively fixed when said actuator element is in saidlocking position, and radially released when said actuator element isreleased for axial movement when said coil is deenergized, and lockingmeans causing axial locking of said control element when saidinterlocking elements are radially positively fixed and axially releasedwhen said locking elements are radially released.
 2. A brake controlleras claimed in claim 1, wherein said locking means includes anintermediate fixed bushing having a wall of predetermine thickness whichis formed with at least two radial holes each receiving an interlockingelement which is greater in a radial dimension than the thickness ofsaid wall of said intermediate bushing, said interlocking elementsretained therein in a fixed radial position by a portion of saidactuating element, located adjacent said interlocking elements with sadactuating element in said locking position, in which condition saidinterlocking elements lock axial movement of said control element, andupon a failure of said anti-locking control, said actuating element, isslid axially and has a portion brought into alignment with said axialshift of said actuating element, said portion formed with a radialrecess capable of accommodating radial movement of said interlockingelements, said axial movement of said control element released by radialmovement of said interlocking elements into said radial recess.
 3. Abrake controller as claimed in claim 2, wherein said actuating elementhas a piston-shaped configuration and said control element surroundssaid intermediate bushing and said actuating element, and said actuatingelement extends through said intermediate bushing.
 4. A brake controlleras claimed in claim 2, wherein said radial recess of said actuatingelement is formed by a circumferential groove with beveled edges.
 5. Abrake controller as claimed in claim 1, wherein said actuating elementis connected to a magnetic armature surrounded by said coil which drawssaid magnetic armature into its magnetic field, and a compression springacting on said armature opposing the force of said magnetic field.
 6. Abrake controller as claimed in claim 1, further including means imposinga control force on said control element, the magnitude of said forcedetermining the reduction in pressure produced by said brake pressurecontroller.
 7. A brake controller as claimed in claim 1, wherein saidbrake controller is a twin-type controller, and further including atransmission element acting on both brake pressure controllers, and inthat said control element acts upon said transmission element.
 8. Abrake controller as claimed in claim 1, further including a housinghaving a chamber free of pressure fluid, at least one control piston,mounted in a stepped bore in said housing filled with pressure fluid,said control piston having one end located within said bore and anotherend projecting into said chamber, said one end of said control pistonhaving a valve closing member and an aligned valve seat having anopening positioned within a cavity in said one end of said controlpiston, a compression spring carried by sad control piston urging saidvalve closing member toward said valve seat, a tappet abutted againstsaid valve closing member, said tappet having one end projecting throughsaid valve seat opening out of said one end of said control piston, anend wall of sad bore located to be engaged by said projecting one end ofsaid tappet to move said valve closing member away from said valve seatto maintain said valve seat opening clear when said controller islocked.
 9. A brake controller as claimed in claim 8, wherein saidcontrol piston is axially movable slightly when said controller islocked, said movement smaller than the extent of travel of said valveclosing member required to be seated on said valve seat opening.
 10. Abrake controller as claimed in claim 8, wherein said bore is formed withan outlet-side section containing said one end of said control piston,means for reducing the outlet-side pressure within said section of saidbore by an increase of the volume thereof when said anti-locking controlfails.